Method of improving the north seeking result

Details Method of improving the north seeking result Method of improving the north seeking result

1991-02-20

1992-06-02

Haroian, Harry N.

Geometrical instruments

Indicator of direction of force traversing natural media

Gyroscopically controlled or stabilized

G01C 1938

Patent

active

051175592

DESCRIPTION:

BRIEF SUMMARY
PROBLEM AND PRIOR ART

North-seeking or north-determining gyros (NSG) usually serve to determine the direction of mobile equipment (vehicles, directional antennas, tunnel heading and cutting machines, geodetic instruments, etc.) and are subject to more or less heavy interference movements during the north-seeking process even if the vehicle is not moving. Methods are known (for example, from DE-OS [German Laid-Open Patent Application]3,346,450) to reduce the sensitivity to rotary interfering movements, for example with the aid of a further sensor. In real system applications, the interfering movements lie within a very broad frequency range and their amplitude often exceeds the useful signal by many orders of magnitude; however, at the same time, high measuring accuracy is required during a short measuring period (e.g., only 1 to 2 minutes)
Prior art filtering methods do not always furnish sufficiently accurate results. The measuring accuracy becomes poorer, in particular, for greater interfering movements and with increasing geographic latitude since then the usable earth rotation component decreases.
Depending on the interfering movement, a more or less noise encumbered north-seeking result is available at the output of the north-seeking gyro. The noise amplitude increases with increasing geographic latitude. The noise process is generally not stationary, that is the noise amplitude changes over time; noisy phases alternate with quieter sections, low-frequency sections alternate with higher frequency sections.


ADVANTAGES OF THE INVENTION

This signal is now subjected to digital filtering including the features of claim 1. This filter, called a "window algorithm" selects particularly the quieter phases and filters out accurate measuring results as a function of filter criteria.
The filtering method according to claim 1 can be improved further by pre-filtering methods according to claims 2 and 3. Further modifications result from the further dependent claims. The procedure results in a number of advantages, namely: adaptation to a very broad noise spectrum; the filter criteria (N; .DELTA..gamma.); accuracy is independent of noise spectrum and geographic latitude; process; criteria are not met at the end of the permissible time Tmax; result with less accuracy; provides information with respect to the accuracy.


DESCRIPTION OF THE DRAWING FIGURES

Embodiments of the invention will be described with reference to the drawing figures.
It is shown in:
FIG. 1, the configuration of a north-seeking gyro;
FIG. 2, a block circuit diagram of the filter arrangement;
FIG. 3, diagrams;
FIG. 4, diagrams to explain the error compensation by means of the accelerometer signal;
FIG. 5, diagrams to explain the main filtering by means of the time window.
FIG. 1 shows the configuration of the gyro: a gas bearing rate gyro 1 is installed together with an accelerometer 2 in a frame 3 rotatable about the elevation axis. The elevated frame 3 can be rotated about an angle .alpha. by means of a servomotor 4, e.g. a stepping motor, so that the measuring axes of the gyro and of the accelerometer can be pivoted into discrete directions.
The arrangement is described in greater detail in DE-OS 3,346,450.
FIG. 2 is a block circuit diagram of the filter. The reference numeral 11 identifies a north-determining gyro (a gyro that can be rotated into several positions) including an evaluation circuit. Block 11 is intended to put out measurement signals (angular velocities) at given time intervals T. The reference numeral 12 identifies an accelerometer which also puts out measurement signals at time intervals T. Both signals are fed to filters 13 and 14 which filter out higher frequency noise components. The average of the pre-filtered gyro measurement values is formed in a block 15 over a time period T.sub.K and this average is stored in a memory 16. At the beginning and end of period T.sub.K, the averages A.sub.a and A.sub.e of the accelerometer output signal are formed in a block 17 at intervals T.sub.B and the difference (A.sub.e -A.sub.a)

Affiliated with

Also associated with

Rating

Method of improving the north seeking result does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method of improving the north seeking result, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of improving the north seeking result will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2220944